The present invention relates to a portable waste disposal system that is adapted primarily for use in marine craft, mobile homes, trailers and the like.
Due to increasingly strict federal and state environmental regulations, it has become necessary to avoid the discharge of untreated sewage from boats and other vehicles, as well as the indiscriminate disposal of sewage in any environment, even remote and rural areas. Present day air pollution standards have also made the discharge of noxious odors into the atmosphere illegal in many areas. In addition, a general increased concern over the environment has made the disposal of raw sewage and the discharge of offensive odors extremely undesirable.
Many procedures have been proposed for the disposal of sewage under such difficult conditions as exist where the sanitary facilities are carried by vehicles. The use of heat to vaporize the liquid effluent from the source of sewage, or from an intermediate septic tank, has been proposed. In some instances, waste heat from an internal combustion engine or other heat source carried by the vehicle has been employed. Boilers and vaporization chambers have also been utilized into which the sewage or liquid effluent is directly introduced. However, with such systems, the minerals and organic solids in the effluent eventually form a caked deposit on the internal walls of the boilers or vaporization chambers, thus acting as a heat insulator, and greatly reducing the volume of the boiler and the efficiency of the heat transfer to the boiler walls. Consequently, the boiler is no longer capable of operating at optimum efficiency, and may also be incapable of vaporizing waste material at the required rate. The reduced operating temperature can also result in the creation of noxious odors in greater quantity.
A typical waste disposal system currently used in many marine craft simply comprises an incinerator unit located directly beneath the toilet for receiving the waste material. The system is operated simply by closing a hatch located at the top of the unit and activating a burner which incinerates the excrement for a predetermined period of time. After several operations of the system, the incinerator must be cleaned through the same hatch; which can be a very unpleasant and tedious task.
The present invention seeks to overcome the disadvantages of these prior art systems by providing a portable waste disposal system that operates completely automatically, generates no offensive odors, requires infrequent cleaning and is easy to clean. In addition, the present system is adapted to incinerate the waste material as completely as possible so that a minimum amount of solid waste material is left unconverted. In particular, the present invention is adapted to produce only approximately 15 grams of solid matter for every gallon of excrement disposed. Consequently, on the average, clean out of the system is required only every 14 days when continuously in use. In addition, the system can dispose of approximately one gallon of excrement every hour, which is sufficient to accommodate the excrement of as many as 8 adults on a continuous basis when a flush efficient marine type toilet is used.
In general, the present system comprises a macerator unit for converting the excrement to a liquified effluent, and an incinerator unit for incinerating the liquified effluent. The macerator unit comprises a tank that is divided into a holding compartment and a feed compartment. Excrement is supplied through a waste inlet into the holding compartment from where it is macerated and provided to the feed compartment. A liquid circulation pump draws the effluent from the feed compartment and pumps the effluent to the incinerator unit, which may be located at a point on the craft or vehicle quite remote from the macerator unit.
The incinerator unit essentially comprises a combustion chamber having a crucible disposed therein for receiving the effluent. Controlled amounts of effluent are supplied to the combustion chamber by a feed pump which draws effluent from the circulation line supplied by the liquid circulation pump from the macerator unit. A high temperature burner is mounted on the top of the combustion chamber that is adapted to generate a downwardly directed flame which engulfs the entire combustion chamber. The fuel for the burner is provided by a fuel pump and is regulated by a pair of fuel valves. The primary fuel valve is adapted to provide a minimum amount of fuel to the burner, and the secondary fuel valve is cycled between its open and closed position in accordance with the temperature of the exhaust gases from the combustion chamber. In this manner, the temperature of the incineration process can be controlled within preselected temperature parameters to optimize the incineration process and prevent the production of offensive odors. The effluent within the combustion chamber is incinerated until all of the liquid has been vaporized and the remaining solid matter has been reduced to a fine ash. The latter part of the incineration cycle, or burn-out cycle, is conducted with a reduced fuel-to-air mixture so that the remaining solid waste matter is completely oxidized. In this manner, only a minimum amount of solid waste matter remains after the completed incineration cycle. In addition, by completely oxidizing the solid matter to a fine ash, the crucible can be readily emptied of the remaining ash material simply by rotating the crucible to dump the material to the floor of the chamber. From there, the ash material is easily removed from the unit via a convenient ash removal duct located at the rear of the unit. In this manner, the continuous buildup or caking of the effluent within the incinerator unit is avoided.
The incinerator unit is cooled by a pair of forced draft fans which circulate ambient air through a pair of cooling chambers which completely surround the combustion chamber. The air from the cooling chambers is then mixed with the exhaust gases from the combustion chamber to cool the exhaust gases before being expelled from the incinerator unit. In addition to providing cooling for the combustion chamber, the fans also serve other cooling functions. In particular, the primary cooling fan draws ambient air through the control compartment to dissipate the heat from the electronic control unit, and also directs cooling air along the shaft connecting the pot rotator motor to the crucible within the combustion chamber. In this manner, the motor is protected from the intense heat of the combustion chamber which would otherwise be transmitted along the shaft and cause the motor to overheat.
Similarly, the combustion fan, in addition to drawing ambient air around the combustion chamber, provides the air supply for the burner, and also supplies cooling air along the effluent feed line into the combustion chamber to cool the feed line and prevent the heat from the combustion chamber from causing the effluent to cake within the feed line.
The entire waste disposal system is operated and controlled by a solid state electronic control unit comprising a d.c. battery powered logic and timing unit and a high current, high voltage transistor switching panel supplying d.c. generator or rectified a.c. power to the various mechanical components. In addition to controlling the entire sequence of events which occur during the system's operation, the control circuit continuously performs various safety checks to insure that the system is operating within specified critical parameters. If at any time a condition arises which does not fit within these parameters, the control circuit automatically enters an emergency shutdown sub-routine which effectively deactivates the entire system, except for the fans, which continue to operate until the system has cooled to a safe level.